This invention relates to astrophotography in general and more particularly to the use of what is referred to as "cold cameras" as attachments to astronomical telescopes.
There has been a relatively recent revival in the use of cold cameras wherein the film is maintained at a low temperature to inhibit latent image decay, thereby avoiding the necessity of using prolonged exposure times. The major problem with use of cold cameras is the precipitation of ice particles on the film resulting from the freezing of moisture in the ambient air to which the film is exposed. At the present time, there are three basic known types of cold cameras, which deal with the moisture problem. These known cameras are referred to as (1) vacuum cold cameras, (2) dry air cold cameras and (3) plug cold cameras. In the vacuum cold camera, a pump evacuates the air and moisture entrained therein from the film chamber. Aside from its expense, use of a vacuum pump is bothersome and sometimes unreliable. In the dry air cold camera, dry air or nitrogen is used to flush the film chamber. This method is fully effective only in dry climates. In the plug cold camera, a plastic plug is used to displace air adjacent the film. However, the use of the plug inhibits rapid and effective freezing of the film and reduces the light-gathering power. Because of the constructional arrangements associated with cold cameras of the foregoing types, film must be loaded in the dark. Further, the moisture removal procedure must be frequently repeated.
It is therefore an important object of the present invention to provide a cold camera within which a moisture free atmosphere is maintained without the aforementioned drawbacks associated with existing cold cameras. In accordance with the foregoing objects, it is a particular object of the present invention to enable loading of a cold camera in daylight and to provide a cold camera in which multiple exposures may be obtained without unloading and reconditioning the interior of the camera.